Aquaporin-4 Peptides, Compositions and Methods of Use

ABSTRACT

The present disclosure provides human Aquaporin 4 (AQP4) peptides and peptides having homology to human Aquaporin 4 (AQP4) peptides. Also provided herein are methods for using human AQP4 peptides and peptides homologous to human AQP4 peptides for diagnosing and/or treating Neuromyelitis Optica.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit to U.S. Provisional Application Ser. No. 61/735,675, filed Dec. 11, 2012, the disclosure of which is herein incorporated by reference in its entirety.

GOVERNMENT SUPPORT

This inventions was made with government support under Grant Nos. AI073737, AI059709, NS063008, and GM073210 awarded by the National Institutes of Health. The federal government has certain rights in this invention.

TECHNICAL FIELD

This present disclosure relates to peptides having homology to human Aquaporin 4 (AQP4) peptides and peptides having homology to human Aquaporin-4 (AQP-4) peptides and the use of theses peptides in diagnosing, and/or treating neuromyelitis optica (NMO).

INTRODUCTION

Neuromyelitis optica (NMO), or Devic's disease, is an autoimmune, inflammatory disorder of the optic nerves and spinal cord. The main symptoms of Devic's disease are loss of vision and spinal cord function. As for other etiologies of optic neuritis, the visual impairment usually manifests as decreased visual acuity, although visual field defects, or loss of color vision can occur in isolation or prior to formal loss of acuity. Spinal cord dysfunction can lead to muscle weakness, reduced sensation, or loss of bladder and bowel control. The damage in the spinal cord can range from inflammatory demyelination to necrotic damage of the white and grey matter. The inflammatory lesions in Devic's disease have been classified as type II lesions (complement mediated demyelination).

Attacks optic neuritis and transverse myelitis suffered by NMO patients are treated with short courses of high dosage intravenous corticosteroids such as methylprednisolone IV. When attacks progress or do not respond to corticosteroid treatment, plasmapheresis can be used. Commonly used immunosuppressant treatments include azathioprine (Imuran) plus prednisone, mycophenolate mofetil plus prednisone, Rituximab, Mitoxantrone, intravenous immunoglobulin (WIG), and Cyclophosphamide.

The disease can be monophasic, i.e., a single episode with permanent remission. However, at least 85% of NMO patients have a relapsing form of the disease with repeated attacks of transverse myelitis and/or optic neuritis. In patients with the monophasic form of NMO, the transverse myelitis and optic neuritis occur simultaneously or within days of each other. On the other hand, patients with the relapsing form of NMO are more likely to have weeks or months between the initial attacks and to have better motor recovery after the initial transverse myelitis event. Relapses usually occur early with about 55% of patients having a relapse in the first year and 90% in the first 5 years.

Studies have suggested a role for T helper 17 (Th17) cells and autoantigens, including aquaporin and myelin proteins in the pathology of NMO. Th17 T cells are a subset of T helper cells, characterized by their production of interleukin 17 (IL-17). They are considered developmentally distinct from Th1 and Th2 cells and excessive amounts of the cells are thought to play a key role in autoimmune disease.

Provided herein are peptides, peptide compositions and methods useful in diagnosing and/or treating NMO.

SUMMARY

The present disclosure provides human Aquaporin 4 (AQP4) peptides and peptides having homology to human Aquaporin 4 (AQP4) peptides. Also provided herein are methods for using human AQP4 peptides and peptides homologous to human AQP4 peptides for diagnosing and/or treating Neuromyelitis Optica.

In certain embodiments, a composition is provided. The composition includes a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: Leu-Pro-X¹-X²-Met-X³-X⁴-Ile-X⁵-X⁶, wherein the peptide is up to 50 amino acids in length, and wherein X¹ is Val (V) or Ile (I), X² is Ser (S) or Asp (D), X³ is Val (V), Ile (I), or Gly (G), X⁴ is Leu (L) or Ile (I), X⁵ is Met (M) or Ser (S), and X⁶ is Leu (L), Val (V), or Ala (A). In certain embodiments, X¹ is Val (V), X² is Ser (S) or Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L).

In another embodiment, a composition that includes a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: LPVXMVLISL, wherein the peptide is up to 50 amino acids in length, and wherein X is Asp or Ser, is provided.

In another embodiment, a composition that includes a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: GILYLVTPPSVVGGLGVTMV, wherein the peptide is up to 50 amino acids in length, is provided.

In another embodiment, a composition that includes a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: SMNPARSFGPAVIMGNWENH, wherein the peptide is up to 50 amino acids in length, is provided.

In another embodiment, a composition that includes a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: AGHGLLVELIITFQL, wherein the peptide is up to 50 amino acids in length, is provided.

In another embodiment, a composition that includes a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: RFKEAFSKAAQQTKGSYMEV, wherein the peptide is up to 50 amino acids in length, is provided.

In certain embodiments, the peptide may be 5-30 amino acids in length. In some embodiments, the peptide may be 10-20 amino acids in length.

In certain embodiments, a method of diagnosing Neuromyelitis Optica (NMO) in a subject is disclosed. The method may include contacting a sample from the subject with a peptide as disclosed herein; and measuring the number of T cells, wherein an increase in the number of T cells as compared to a control indicates that the subject has NMO.

In certain cases, the T cells may be T helper 17 (Th17) T cells. In certain cases, the T cells may be CD4⁺ T cells. The peptide may be 5-30 amino acids in length. In certain cases, the peptide may be 10-20 amino acids in length.

In certain embodiments, a method for screening for candidate agents for inhibiting proliferation of T cells is provided. The method includes contacting a T cell obtained from a subject having Neuromyelitis Optica with a peptide as provided above, and a candidate agent; measuring the number of T cells, wherein a decrease in the number of T cells as compared to a control indicates that the candidate agent inhibits proliferation of T cells. In certain embodiments, the T cells may be T helper 17 (Th17) T cells. In certain embodiments, the T cells may be CD4⁺ T cells. The peptide may be 5-30 amino acids in length. In certain cases, the peptide may be 10-20 amino acids in length.

A method for inducing immune tolerance to AQP-4 protein and fragments thereof in a subject is also provided. The method includes administering an effective dose of the composition set forth above to a subject, wherein the administering the peptide induces immune tolerance to AQP-4 protein and fragments thereof in the subject. The peptide may be 5-30 amino acids in length. In certain cases, the peptide may be 10-20 amino acids in length.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-1F shows that T cells from NMO patients recognize discrete determinants of AQP4.

FIG. 2A-2C shows that HLA-DR serves as a restriction element for AQP4-specific T cells.

FIG. 3A-3E illustrates the cross-reactivity between AQP4 p63-76 and Clostridium perfringens ABC transporter permease (ABC/TP) p204-217.

FIG. 4A-4D shows that AQP4 p61-80-specific T cells exhibit a pro-inflammatory bias.

FIG. 5A-5C shows CD14+ monocytes from NMO patients exhibit increased expression of certain co-stimulatory molecules and production of IL-6.

FIG. 6 provides the amino acid sequence of human AQP-4 protein (GenBank Accession No. AAH22286.1).

FIG. 7 provides the amino acid sequence of ABC-transporter permease protein of Clostridium perfringens (NCBI Reference Sequence: ZP_(—)02952885.1).

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present disclosure provides human Aquaporin 4 (AQP4) peptides and peptides having homology to human Aquaporin 4 (AQP4) peptides. Also provided herein are methods for using human AQP4 peptides and peptides homologous to human AQP4 peptides for diagnosing and/or treating Neuromyelitis Optica.

Before the present invention and specific exemplary embodiments of the invention are described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. To the extent such publications may set out definitions of a term that conflicts with the explicit or implicit definition of the present disclosure, the definition of the present disclosure controls.

It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a sample” includes a plurality of samples and reference to “a peptide” includes reference to one or more peptides, and so forth.

The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

DEFINITIONS

The phrase “Aquaporin-4 (AQP-4) peptides” as used herein refers to peptides that are derived from amino acid sequence of human aquaporin-4. As such, AQP-4 peptides include peptides comprising a contiguous amino acid sequence that is identical to a contiguous amino acid sequence found in amino acid sequence of human aquaporin-4 (GenBank Accession No. AAH22286.1). An AQP-4 peptide may be 5-50 amino acids in length.

The phrase “AQP-4 homologous peptide” or a grammatical equivalent thereof, as used herein, refers to peptides that include a contiguous amino acid sequence that is at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% identical to a contiguous amino acid sequence found in amino acid sequence of human AQP-4 protein. For example, a twenty amino acids long peptide that is at least 50% at least 60%, at least 70%, at least 80%, or at least 90% identical to a contiguous amino acid sequence found in amino acid sequence of human aquaporin-4 is an example of an AQP-4 homologous peptide.

The term “unit dosage form”, as used herein, refers to physically discrete units suitable as unitary dosages for human and animal subjects, each unit containing a predetermined quantity of peptide(s) disclosed herein calculated in an amount sufficient to produce the desired effect in association with a pharmaceutically acceptable diluent, carrier or vehicle. The specifications for the unit dosage forms may depend on the particular peptide employed and the effect to be achieved, and the pharmacodynamics associated with each peptide in the host.

An “immunogen” is capable of inducing an immunological response against itself on administration to a mammal or due to autoimmune disease.

The terms “treatment”, “treating”, “treat” and the like are used herein to generally refer to obtaining a desired pharmacologic and/or physiologic effect. The effect may be prophylactic in terms of completely or partially preventing a disease or symptom thereof and/or may be therapeutic in terms of a partial or complete stabilization or cure for a disease and/or adverse effect attributable to the disease. “Treatment” as used herein refers to any treatment of a disease in a mammal, particularly a human, and includes: (a) preventing the disease or symptom from occurring in a subject which may be predisposed to the disease or symptom but has not yet been diagnosed as having it; (b) inhibiting the disease symptom, i.e., arresting its development; or (c) relieving the disease symptom, i.e., causing regression of the disease or symptom.

The terms “individual”, “subject”, “host”, and “patient”, are used interchangeably herein and refer to any mammalian subject for whom diagnosis, treatment, or therapy is desired, particularly humans. Mammals other than humans can be advantageously used as subjects that represent animal models of inflammation. A subject can be male or female.

The term “a sample” as used herein refers to any biological sample that is isolated from a subject. A sample can include, without limitation, a single cell or multiple cells or cell fragments, such as, platelets, red blood cells, white blood cells or leucocytes, such as lymphocytes, e.g., B cell, T cells, endothelial cells, cell lysates, such as, whole cell lysates or a fraction of cell lysate; an aliquot of body fluid, whole blood, serum, plasma, synovial fluid, lymphatic fluid, ascites fluid, and interstitial or extracellular fluid; tissue biopsies. “Blood sample” can refer to whole blood or any fraction thereof, including blood cells, red blood cells, white blood cells or leucocytes, platelets, serum and plasma. Samples can be obtained from a subject by means including but not limited to venipuncture, biopsy, needle aspirate, scraping, surgical incision, or intervention or other means known in the art.

An “isolated” peptide is one which has been separated and/or recovered from a component of the environment in which it was produced. Contaminant components of its production environment are materials which would interfere with screening, diagnostic or therapeutic uses for the peptide, and may include chemicals, enzymes, hormones, and other proteinaceous or nonproteinaceous components. In certain cases, the peptides of the present disclosure are produced synthetically, for example, by chemical synthesis. In certain embodiments, the peptides are purified using standard purification procedures known in the art. Ordinarily, isolated peptide may be prepared by at least one purification step.

The term “agent” as used in the context of candidate agent refers to a chemical compound, a mixture of chemical compounds, a biological macromolecule, or an extract made from biological materials.

The term “effective amount” refers to an amount of a biologically active molecule or conjugate or derivative thereof sufficient to exhibit a detectable therapeutic effect without undue adverse side effects (such as toxicity, irritation and allergic response) commensurate with a reasonable benefit/risk ratio. The effective amount for a patient may depend upon the type of patient, the patient's size and health, the nature and severity of the condition to be treated, the method of administration, the duration of treatment, the nature of concurrent therapy (if any), the specific formulations employed, and the like. The effective amount for a given subject can be determined by one of ordinary skill in the art using routine experimentation based on the information provided herein.

As used herein, the term “concurrent therapy” is used interchangeably with the terms “combination therapy” and “adjunct therapy”, and will be understood to mean that the patient in need of treatment is treated or given another drug for the disease/disorder in conjunction with the compositions of the present disclosure. This concurrent therapy can be sequential therapy where the patient is treated first with one drug and then the other, or the two drugs are given simultaneously

The term “pharmaceutically acceptable” refers to peptides and compositions containing peptides which are suitable for administration to humans and/or animals without undue adverse side effects such as toxicity, irritation and/or allergic response commensurate with a reasonable benefit/risk ratio.

The compositions comprising peptides disclosed herein may be administered to a patient by any method known in the art, including but not limited to, oral, topical, transdermal, parenteral, subcutaneous, intranasal, intramuscular, intraperitoneal, intravenous, intraocular, intravitreal, sub-retinal routes, including both local and systemic applications. In addition, the peptides disclosed herein may be formulated to provide delayed, controlled or sustained release using formulation techniques which are well known in the art.

Overview

The present disclosure provides peptides, including AQP-4 peptides derived from human AQP-4 protein and peptides homologous to AQP-4 peptides. As shown herein, AQP-4 peptide p61-80 includes a core sequence p63-76 (EKPLPVDMVLISLC) which is a T cell epitope. Peptides containing this core sequence or a sequence having at least 60% identity to the amino acid sequence of this core sequence result in proliferation of AQP-4 specific T cells in NMO patients.

Peptides

In certain embodiments, the present disclosure provides AQP-4 peptides and peptides homologous to AQP-4 peptides.

For example, examples of ABC-TP proteins from strains of Clostridium perfringens, Clostridium scindens, Clostridium sporogens, and Clostridium hylemonae are aligned in Table 1 over a region having sequence identity with an example of an AQP4 peptide, p66-75 (LPVDMVLISL).

TABLE 1 % Homology with AQP4 p66-75 AQP4 p66-75 L P V D M V L I S L C. perfringens L P V S M V L I S L 90% Commensal and pathogenic C. Scindens L P V S M G L I S V 70% Commensal C. Sporogenes L P V S M I I I M L 60% Pathogenic C. Hylemonae L P I S M G L I S A 60% Commensal

Accordingly, AQP-4 peptides comprise a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-X¹-X²-Met-X³-X⁴-Ile-X⁵-X⁶  (Formula I)

-   -   wherein X¹, X², X³, X⁴, X⁵, and X⁶ are any amino acid, and     -   wherein the peptide is up to 50 amino acids in length.

In certain embodiments, X¹ is Val (V) or Ile (I). In certain embodiments, X² is Ser (S) or Asp (D). In certain embodiments, X³ is Val (V), Ile (I), or Gly (G). In certain embodiments, X⁴ is Leu (L) or Ile (I). In certain embodiments, X⁵ is Met (M) or Ser (S). In certain embodiments, X⁶ is Leu (L), Val (V), or Ala (A). In certain embodiments, X¹ is Val (V), X² is Ser (S) or Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In certain embodiments, X¹ is Val (V), X² is Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Asp-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Val (V). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Gly-Leu-Ile-Ser-Val.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Ile (I), X⁴ is Ile (I), X⁵ is Met (M), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Ile-Ile-Ile-Met-Leu.

In certain embodiments, X¹ is Ile (I), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Ala (A). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Ile-Ser-Met-Gly-Leu-Ile-Ser-Ala.

Examples of suitable embodiments include where:

X¹ is Val and X² is Ser, X¹ is Val and X² is Asp, X¹ is Val and X³ is Val, X¹ is Val and X³ is Gly, X¹ is Val and X³ is Ile, X¹ is Val and X⁴ is Leu, X¹ is Val and X⁴ is Ile, X¹ is Val and X⁵ is Ser, X¹ is Val and X⁵ is Met, X¹ is Val and X⁶ is Leu, X¹ is Val and X⁶ is Val, X¹ is Val and X⁶ is Ala, X¹ is Ile and X² is Ser, X¹ is Ile and X² is Asp, X¹ is Ile and X³ is Val, X¹ is Ile and X³ is Gly, X¹ is Ile and X³ is Ile, X¹ is Ile and X⁴ is Leu, X¹ is Ile and X⁴ is Ile, X¹ is Ile and X⁵ is Ser, X¹ is Ile and X⁵ is Met, X¹ is Ile and X⁶ is Leu, X¹ is Ile and X⁶ is Val, X¹ is Ile and X⁶ is Ala, X² is Ser and X³ is Val, X² is Ser and X³ is Gly, X² is Ser and X³ is Ile, X² is Ser and X⁴ is Leu, X² is Ser and X⁴ is Ile, X² is Ser and X⁵ is Ser, X² is Ser and X⁵ is Met, X² is Ser and X⁶ is Leu, X² is Ser and X⁶ is Val, X² is Ser and X⁶ is Ala, X² is Asp and X³ is Val, X² is Asp and X³ is Gly, X² is Asp and X³ is Ile, X² is Asp and X⁴ is Leu, X² is Asp and X⁴ is Ile, X² is Asp and X⁵ is Ser, X² is Asp and X⁵ is Met, X² is Asp and X⁶ is Leu, X² is Asp and X⁶ is Val, X² is Asp and X⁶ is Ala, X³ is Val and X⁴ is Leu, X³ is Val and X⁴ is Ile, X³ is Val and X⁵ is Ser, X³ is Val and X⁵ is Met, X³ is Val and X⁶ is Leu, X³ is Val and X⁶ is Val, X³ is Val and X⁶ is Ala, X³ is Gly and X⁴ is Leu, X³ is Gly and X⁴ is Ile, X³ is Gly and X⁵ is Ser, X³ is Gly and X⁵ is Met, X³ is Gly and X⁶ is Leu, X³ is Gly and X⁶ is Val, X³ is Gly and X⁶ is Ala, X³ is Ile and X⁴ is Leu, X³ is Ile and X⁴ is Ile, X³ is Ile and X⁵ is Ser, X³ is Ile and X⁵ is Met, X³ is Ile and X⁶ is Leu, X³ is Ile and X⁶ is Val, X³ is Ile and X⁶ is Ala, X⁴ is Leu and X⁵ is Ser, X⁴ is Leu and X⁵ is Met, X⁴ is Leu and X⁶ is Leu, X⁴ is Leu and X⁶ is Val, X⁴ is Leu and X⁶ is Ala, X⁴ is Ile and X⁵ is Ser, X⁴ is Ile and X⁵ is Met, X⁴ is Ile and X⁶ is Leu, X⁴ is Ile and X⁶ is Val, X⁴ is Ile and X⁶ is Ala, X⁵ is Ser and X⁶ is Leu, X⁵ is Ser and X⁶ is Val, X⁵ is Ser and X⁶ is Ala, X⁵ is Met and X⁶ is Leu, X⁵ is Met and X⁶ is Val, and X⁵ is Met and X⁶ is Ala.

In certain embodiments, the AQP-4 peptide may comprise a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-X-Met-Val-Leu-Ile-Ser-Leu  (Formula II)

wherein X is any amino acid.

In some such embodiments, X is Ser (S) or Asp (D). As such, in some embodiments, X is Ser (S) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVSMVLISL. In some embodiments, X is Asp (D) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVDMVLISL.

In certain embodiments, the peptide may comprise an amino acid sequence having at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% sequence identity to a contiguous stretch of amino acids in the sequence of AQP-4 peptide p63-76 (EKPLPVDMVLISLC), wherein the peptide is up to 50 amino acids in length. As used herein, p63-76 in the context of AQP-4 peptide refers to a peptide having the amino acids sequence of amino acid starting at position 63 and ending at position 76 of human AQP-4 protein sequence shown in FIG. 6.

In certain embodiments, the peptide may include a contiguous stretch of ten amino acids having at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% sequence identity to a contiguous stretch of ten amino acids in the sequence of AQP-4 peptide p63-76. In certain embodiments, the peptide may include a contiguous stretch of ten amino acids having at least 70%, or at least 80% sequence identity to a contiguous stretch of ten amino acids of AQP-4 peptide p63-76. In certain embodiments, the peptide may include a contiguous stretch of ten amino acids having at least 90% sequence identity to a contiguous stretch of ten amino acids of AQP-4 peptide p63-76.

In certain embodiments, the peptide may include a contiguous stretch of ten amino acids having at least 70% sequence identity to the amino acid sequence of AQP-4 peptide p66-75 (LPVDMVLISL). In certain embodiments, the peptide may include a contiguous stretch of ten amino acids having at least 80% sequence identity to the amino acid sequence of AQP-4 peptide p66-75. In certain embodiments, the peptide may include a contiguous stretch of ten amino acids having at least 90% sequence identity to the amino acid sequence of AQP-4 peptide p66-75. As used herein, p66-75 in the context of AQP-4 peptide refers to a peptide having the amino acids sequence of amino acid starting at position 66 and ending at position 75 of human AQP-4 protein sequence shown in FIG. 6.

In certain embodiments, the peptide may be AQP-4 peptide including the AQP-4 p61-80 sequence. In certain embodiments, the peptide may be AQP-4 p61-80 peptide. As used herein, p61-80 in the context of AQP-4 peptide refers to a peptide having the amino acids sequence of amino acid starting at position 61 and ending at position 80 of human AQP-4 protein sequence shown in FIG. 6. In certain embodiments, the peptide may be AQP-4 p63-76 peptide. In certain embodiments, the peptide may be AQP-4 p66-75 peptide (LPVDMVLISL).

In certain embodiments, the peptide may be derived from ABC transporter permease (ABC-TP) protein of a Clostridium species. In certain cases, the peptide may be a peptide derived from ABC-TP protein from a strain of bacterium in the genus Clostridium (e.g., Clostridium perfringens, Clostridium scindens, Clostridium sporogens, Clostridium hylemonae, and the like). For example, in certain cases, the peptide may be a peptide derived from ABC-TP protein having the accession no. ZP_(—)02952885.1, ZP_(—)02638213.1, ZP_(—)02634520.1, ZP_(—)02630305.1, ZP_(—)02431563, ZP_(—)02995934, or ZP_(—)03776873.1). In certain cases, the peptide may include a sequence of ABC-TP protein derived peptide p204-217 (FIILPVSMVLISLV). As used herein, p204-217 in the context of AQP-4 peptide refers to a peptide having the amino acids sequence of amino acid starting at position 204 and ending at position 217 of protein sequence shown in FIG. 7. In certain cases, the peptide may include a sequence of ABC-TP protein derived peptide p207-216 (LPVSMVLISL). As used herein, p207-216 in the context of AQP-4 peptide refers to a peptide having the amino acids sequence of amino acid starting at position 207 and ending at position 216 of protein sequence shown in FIG. 7. In certain cases, the peptide may be ABC-TP protein derived peptide p204-217 (FIILPVSMVLISLV). In certain cases, the peptide may be ABC-TP protein derived peptide p207-216 (LPVSMVLISL). In other cases, the peptide may be derived from the expressed or predicted ABC-TP protein in Clostridium species, including commensal bacteria C. scindens and C. hylemonae as well as the pathogenic strain C. sporogenes.

In certain embodiments, the peptide may be 5-50 amino acids long, such as, 5-40 amino acids long, or 5-30 amino acids long, or 5-25 amino acids long, or 5-20 amino acids long, or 5-15 amino acids long, or 10-20 amino acids long, or 10-15 amino acids long. For example, the peptide may be 5 amino acids long, or 7 amino acids long, or 10 amino acids long, or 15 amino acids long, or 20 amino acids long, or 25 amino acids long, or 30 amino acids long, or 35 amino acids long, or 40 amino acids long, or 45 amino acids long, or 50 amino acids long.

In certain embodiments, the peptide may be a peptide up to 50 amino acids in length (for example, up to 40 amino acids long, 30 amino acids long, such as 10-20 amino acids long, or 10-15 amino acids long) and including a contiguous stretch of amino acids having: (i) the sequence of p66-75 (LPVDMVLISL) or (ii) a sequence at least 90% identical to the amino acid sequence LPVDMVLISL.

In certain embodiments, the peptide may be a peptide up to 50 amino acids in length (for example, up to 40 amino acids long, 30 amino acids long, such as 10-20 amino acids long, or 10-15 amino acids long) and including a contiguous stretch of amino acids having: (i) the sequence of p66-75 (LPVDMVLISL), or (ii) the sequence of p207-216 (LPVSMVLISL), (iii) or the sequence of p156-170 (AGHGLLVELIITFQL), (iv) or the sequence of p261-280 (RFKEAFSKAAQQTKGSYMEV).

In certain cases, the peptides may include amino acid substitutions compared to the sequence of p61-80. In certain embodiments, these amino acid substitutions may be conservative substitutions. By conservative substitutions is intended substitution of an amino acid with a similar amino acid, such as those from the following groups: 1) gly, ala; 2) val, ile, leu; asp, glu; 3) asn, gln; 4) ser, thr; 5) lys, arg; and 6) phe, tyr. In certain embodiments, the amino acids substitutions may be guided by the amino acid sequence in AQP-4 protein, predicted AQP-4 protein, or AQP-4 like proteins in other species, such as, mouse, rat, hamster, non-human primates, and macaques. In certain embodiments, the amino acids substitutions may be guided by the amino acid sequence in ABC-TP protein or predicted ABC-TP protein of Clostridium species, such as, Clostridium perfringens, C. scindens, C. hylemonae, and C. sporogenes, for example. Predicted AQP-4 proteins or ABC-TP proteins can be identified by using methods known in the art, such as, by performing sequence search using Basic Local Alignment Search Tool (BLAST) with the amino acid sequence of full length or partial AQP-4 or ABC-TP protein.

In certain cases, the peptide may be an AQP-4 peptide comprising a contiguous stretch of amino acids of peptide p131-150 having the sequence:

GILYLVTPPSVVGGLGVTMV wherein the peptide is up to 50 amino acids in length.

In certain cases, the peptide may be an AQP-4 peptide comprising a contiguous stretch of amino acids of peptide p211-230 having the sequence:

SMNPARSFGPAVIMGNWENH wherein the peptide is up to 50 amino acids in length.

In certain cases, the peptide may be an AQP-4 peptide comprising a contiguous stretch of amino acids of peptide p156-170 having the sequence:

(AGHGLLVELIITFQL), wherein the peptide is up to 50 amino acids in length.

In certain cases, the peptide may be an AQP-4 peptide comprising a contiguous stretch of amino acids of peptide p261-280 having the sequence:

(RFKEAFSKAAQQTKGSYMEV), wherein the peptide is up to 50 amino acids in length.

The peptides disclosed herein may be modified covalently or non-covalently to increase stability of the peptides, such as, increase in vivo half-life, increase bioavailability, or for additional functionality. For example, the peptides may include non-natural amino acids, modifications of the natural amino acids, covalent attachment of a tag, such as, avidin or biotin, or the like.

Also disclosed herein are compositions comprising the peptide(s) provided herein. The composition may include one or more peptide as set forth above. In certain cases, the composition may include a mixture of a plurality of peptides set for the above, such as, 2, 3, 4, 5, 6, 10, 12, 15, 20, or more peptides. The composition may be in solid, semi-solid, liquid or gaseous form, such as, powders, granules, solutions, injections, inhalants, gels, hydrogels, microspheres, etc. In certain cases, the peptide composition may include a diluent, buffer, or other components, such as, water, buffered water, physiological saline, Phosphate Buffered Saline (PBS), Ringer's solution, dextrose solution, and Hank's solution.

In certain cases, a composition comprising a peptide(s) as disclosed above, may be a pharmaceutical composition. Pharmaceutical compositions can include, depending on the formulation desired, pharmaceutically-acceptable, non-toxic carriers or diluents, which are commonly used to formulate pharmaceutical compositions for animal or human administration. The diluent or carrier is selected so as not to affect the biological activity of the combination. Examples of such diluents or carriers are distilled water, buffered water, physiological saline, Phosphate Buffered Saline (PBS), Ringer's solution, dextrose solution, and Hank's solution. In certain embodiments, the pharmaceutical composition or formulation can include other carriers, or other diluents, or adjuvants, or non-toxic, nontherapeutic, nonimmunogenic stabilizers, or excipients and the like. The compositions can also include additional substances to approximate physiological conditions, such as pH adjusting and buffering agents, toxicity adjusting agents, wetting agents and detergents.

The composition can also include any of a variety of stabilizing agents, such as an antioxidant. In certain cases, the peptide can be complexed with various well-known compounds that enhance the in vivo stability of the peptide, or otherwise enhance its pharmacological properties (e.g., increase the half-life of the peptide, reduce its toxicity, enhance solubility or uptake). Examples of such modifications or complexing agents include sulfate, gluconate, citrate and phosphate. The peptides of the composition can also be complexed with molecules that enhance their in vivo attributes. Such molecules include, for example, carbohydrates, polyamines, amino acids, other peptides, ions (e.g., sodium, potassium, calcium, magnesium, manganese), and lipids.

Further guidance regarding formulations that are suitable for various types of administration can be found in Remington's Pharmaceutical Sciences, Mace Publishing Company, Philadelphia, Pa., 17th ed. (1985). For a brief review of methods for drug delivery, see, Langer, Science 249:1527-1533 (1990).

The components used to formulate the pharmaceutical compositions are preferably of high purity and are substantially free of potentially harmful contaminants (e.g., at least National Food (NF) grade, generally at least analytical grade, and more typically at least pharmaceutical grade). Moreover, compositions intended for in vivo use are usually sterile. To the extent that a given compound must be synthesized prior to use, the resulting product is typically substantially free of any potentially toxic agents, particularly any endotoxins, which may be present during the synthesis or purification process.

Diagnosis of NMO

As shown herein, AQP4-specific T cells are present in patient with NMO. Accordingly, the peptides disclosed herein may be used to diagnose NMO in a subject.

In general, a method for diagnosing NMO in a subject comprises contacting a sample from the subject with a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-X¹-X²-Met-X³-X⁴-Ile-X⁵-X⁶  (Formula I)

-   -   wherein X¹, X², X³, X⁴, X⁵, and X⁶ are any amino acid, and     -   wherein the peptide is up to 50 amino acids in length.

In certain embodiments, X¹ is Val (V) or Ile (I). In certain embodiments, X² is Ser (S) or Asp (D). In certain embodiments, X³ is Val (V), Ile (I), or Gly (G). In certain embodiments, X⁴ is Leu (L) or Ile (I). In certain embodiments, X⁵ is Met (M) or Ser (S). In certain embodiments, X⁶ is Leu (L), Val (V), or Ala (A). In certain embodiments, X¹ is Val (V), X² is Ser (S) or Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In certain embodiments, X¹ is Val (V), X² is Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Asp-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Val (V). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Gly-Leu-Ile-Ser-Val.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Ile (I), X⁴ is Ile (I), X⁵ is Met (M), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Ile-Ile-Ile-Met-Leu.

In certain embodiments, X¹ is Ile (I), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Ala (A). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Ile-Ser-Met-Gly-Leu-Ile-Ser-Ala.

Examples of suitable embodiments include where:

X¹ is Val and X² is Ser, X¹ is Val and X² is Asp, X¹ is Val and X³ is Val, X¹ is Val and

X³ is Gly, X¹ is Val and X³ is Ile, X¹ is Val and X⁴ is Leu, X¹ is Val and X⁴ is Ile, X¹ is Val and X⁵ is Ser, X¹ is Val and X⁵ is Met, X¹ is Val and X⁶ is Leu, X¹ is Val and X⁶ is Val, X¹ is Val and X⁶ is Ala, X¹ is Ile and X² is Ser, X¹ is Ile and X² is Asp, X¹ is Ile and X³ is Val, X¹ is Ile and X³ is Gly, X¹ is Ile and X³ is Ile, X¹ is Ile and X⁴ is Leu, X¹ is Ile and X⁴ is Ile, X¹ is Ile and X⁵ is Ser, X¹ is Ile and X⁵ is Met, X¹ is Ile and X⁶ is Leu, X¹ is Ile and X⁶ is Val, X¹ is Ile and X⁶ is Ala, X² is Ser and X³ is Val, X² is Ser and X³ is Gly, X² is Ser and X³ is Ile, X² is Ser and X⁴ is Leu, X² is Ser and X⁴ is Ile, X² is Ser and X⁵ is Ser, X² is Ser and X⁵ is Met, X² is Ser and X⁶ is Leu, X² is Ser and X⁶ is Val, X² is Ser and X⁶ is Ala, X² is Asp and X³ is Val, X² is Asp and X³ is Gly, X² is Asp and X³ is Ile, X² is Asp and X⁴ is Leu, X² is Asp and X⁴ is Ile, X² is Asp and X⁵ is Ser, X² is Asp and X⁵ is Met, X² is Asp and X⁶ is Leu, X² is Asp and X⁶ is Val, X² is Asp and X⁶ is Ala, X³ is Val and X⁴ is Leu, X³ is Val and X⁴ is Ile, X³ is Val and X⁵ is Ser, X³ is Val and X⁵ is Met, X³ is Val and X⁶ is Leu, X³ is Val and X⁶ is Val, X³ is Val and X⁶ is Ala, X³ is Gly and X⁴ is Leu, X³ is Gly and X⁴ is Ile, X³ is Gly and X⁵ is Ser, X³ is Gly and X⁵ is Met, X³ is Gly and X⁶ is Leu, X³ is Gly and X⁶ is Val, X³ is Gly and X⁶ is Ala, X³ is Ile and X⁴ is Leu, X³ is Ile and X⁴ is Ile, X³ is Ile and X⁵ is Ser, X³ is Ile and X⁵ is Met, X³ is Ile and X⁶ is Leu, X³ is Ile and X⁶ is Val, X³ is Ile and X⁶ is Ala, X⁴ is Leu and X⁵ is Ser, X⁴ is Leu and X⁵ is Met, X⁴ is Leu and X⁶ is Leu, X⁴ is Leu and X⁶ is Val, X⁴ is Leu and X⁶ is Ala, X⁴ is Ile and X⁵ is Ser, X⁴ is Ile and X⁵ is Met, X⁴ is Ile and X⁶ is Leu, X⁴ is Ile and X⁶ is Val, X⁴ is Ile and X⁶ is Ala, X⁵ is Ser and X⁶ is Leu, X⁵ is Ser and X⁶ is Val, X⁵ is Ser and X⁶ is Ala, X⁵ is Met and X⁶ is Leu, X⁵ is Met and X⁶ is Val, and X⁵ is Met and X⁶ is Ala.

In certain embodiments, the peptide may comprise a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-X-Met-Val-Leu-Ile-Ser-Leu  (Formula II)

-   -   wherein X is any amino acid.

In some such embodiments, X is Ser (S) or Asp (D). As such, in some embodiments, X is Ser (S) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVSMVLISL. In some embodiments, X is Asp (D) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVDMVLISL.

In certain cases, the method comprises contacting a sample from the subject with a peptide comprising an amino acid sequence having at least 60% sequence identity to the amino acid sequence of a human Aquaphorin-4 (AQP-4) peptide: LPVDMVLISL, wherein the peptide is up to 50 amino acids in length, wherein the sample comprises T cells; and measuring the number of T cells, wherein an increase in the number of T cells as compared to a control indicates that the subject has NMO.

In certain cases, the subject may be exhibiting symptoms of NMO. In other cases, the subject may be asymptomatic but may be predisposed to NMO. In certain embodiments, the subject may have symptoms that are common to NMO and other diseases, such as, multiple sclerosis. In certain cases, the subject may be at an early stage of the disease before all clinical criteria of NMO are evident. In certain cases, the subject may exhibit optic neuritis, myelitis, and at least two of three supportive criteria: (i) MRI evidence of a contiguous spinal cord lesion 3 or more segments in length, (ii) onset brain MRI nondiagnostic for multiple sclerosis, and (iii) NMO-IgG seropositivity. CNS involvement beyond the optic nerves and spinal cord is compatible with NMO (Wingerchuk et al. (2006) Neurology, May 23; 66(10):1485-9)

In certain embodiments, the sample may be a body fluid sample, such as, blood, serum, plasma, cerebrospinal fluid. In certain cases, the sample may be a sample containing Peripheral blood mononuclear cells (PBMC) isolated from the subject. In other cases, the sample may be a sample containing T cells isolated from the subject. In certain cases, the sample may be a solid tissue sample, such as, biopsy sample, for example, sample obtained from brain biopsy, spinal cord biopsy, and the like.

The contacting may be carried out for a period of time sufficient to detect proliferation of T cells. In certain cases, the contacting may be carried out for a period of 1 day to 30 days, such as, 1 day, or 5 days, or 10 days, or 15 days, or 20 days, or 25 days, or 30 days.

An increase in T cell proliferation of at least about 5%, or at least about 10%, or at least about 20%, or at least about 50%, or at least about 70%, or at least about 80%, or at least about 90%, or more, compared to a negative control may indicate that the subject has NMO.

Any suitable negative control may be used for comparison. Suitable negative controls include samples obtained from healthy controls, sample from the subject being diagnosed, where the sample is not contacted with the peptide, for example.

In certain embodiments, T cell proliferation may be compared to a threshold value or range. For example, a normal threshold value or range of T cell proliferation may be determined by contacting the peptides disclosed herein with samples from healthy controls. An increase in T cell proliferation of at least about 5%, or at least about 10%, or at least about 20%, or at least about 50%, or at least about 70%, or at least about 80%, or at least about 90%, or more, compared to the normal threshold value or range may indicate that the subject has NMO.

T cell proliferation may be measured by methods known in the art, such as, the methods disclosed herein.

In certain embodiments, the T cell measured in the method may be a CD4+ T cell. In certain cases, the T cell measured in the method may be a Th17 T cell.

Methods of Screening

A method for screening for candidate agents for inhibiting proliferation of T cells in response to exposure to a peptide disclosed herein is also provided. As shown herein, T cells from NMO patients proliferate when exposed to a peptide comprising an amino acid sequence having at least 60% sequence identity to the amino acid sequence of a human Aquaphorin-4 (AQP-4) peptide LPVDMVLISL. Moreover, an increased frequency of these T cells are Th17 cells which may lead to NMO pathogenesis. Accordingly, the identification of agents that may inhibit the AQP-4 peptide or peptide homologous to AQP-4 peptide mediated proliferation of T cells may be useful in treating NMO.

In general, the method for screening for inhibitors of proliferation of T cells comprises contacting a sample from the subject with: (i) a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-X¹-X²-Met-X³-X⁴-Ile-X⁵-X⁶  (Formula I)

-   -   wherein X¹, X², X³, X⁴, X⁵, and X⁶ are any amino acid, and         wherein the peptide is up to 50 amino acids in length; and     -   (ii) a candidate agent and evaluating the number of T cells,     -   wherein a decrease in the number of T cells as compared to a         control indicates that the candidate agent inhibits         proliferation of T cells. In certain embodiments, X¹ is Val (V)         or Ile (I). In certain embodiments, X² is Ser (S) or Asp (D). In         certain embodiments, X³ is Val (V), Ile (I), or Gly (G). In         certain embodiments, X⁴ is Leu (L) or Ile (I). In certain         embodiments, X⁵ is Met (M) or Ser (S). In certain embodiments,         X⁶ is Leu (L), Val (V), or Ala (A). In certain embodiments, X¹         is Val (V), X² is Ser (S) or Asp (D), X³ is Val (V), X⁴ is Leu         (L), X⁵ is Ser (S), and X⁶ is Leu (L).

In certain embodiments, X¹ is Val (V), X² is Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Asp-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L),

X⁵ is Ser (S), and X⁶ is Val (V). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Gly-Leu-Ile-Ser-Val.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Ile (I), X⁴ is Ile (I), X⁵ is Met (M), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Ile-Ile-Ile-Met-Leu.

In certain embodiments, X¹ is Ile (I), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Ala (A). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Ile-Ser-Met-Gly-Leu-Ile-Ser-Ala.

Examples of suitable embodiments include where:

X¹ is Val and X² is Ser, X¹ is Val and X² is Asp, X¹ is Val and X³ is Val, X¹ is Val and X³ is Gly, X¹ is Val and X³ is Ile, X¹ is Val and X⁴ is Leu, X¹ is Val and X⁴ is Ile, X¹ is Val and X⁵ is Ser, X¹ is Val and X⁵ is Met, X¹ is Val and X⁶ is Leu, X¹ is Val and X⁶ is Val, X¹ is Val and X⁶ is Ala, X¹ is Ile and X² is Ser, X¹ is Ile and X² is Asp, X¹ is Ile and X³ is Val, X¹ is Ile and X³ is Gly, X¹ is Ile and X³ is Ile, X¹ is Ile and X⁴ is Leu, X¹ is Ile and X⁴ is Ile, X¹ is Ile and X⁵ is Ser, X¹ is Ile and X⁵ is Met, X¹ is Ile and X⁶ is Leu, X¹ is Ile and X⁶ is Val, X¹ is Ile and X⁶ is Ala, X² is Ser and X³ is Val, X² is Ser and X³ is Gly, X² is Ser and X³ is Ile, X² is Ser and X⁴ is Leu, X² is Ser and X⁴ is Ile, X² is Ser and X⁵ is Ser, X² is Ser and X⁵ is Met, X² is Ser and X⁶ is Leu, X² is Ser and X⁶ is Val, X² is Ser and X⁶ is Ala, X² is Asp and X³ is Val, X² is Asp and X³ is Gly, X² is Asp and X³ is Ile, X² is Asp and X⁴ is Leu, X² is Asp and X⁴ is Ile, X² is Asp and X⁵ is Ser, X² is Asp and X⁵ is Met, X² is Asp and X⁶ is Leu, X² is Asp and X⁶ is Val, X² is Asp and X⁶ is Ala, X³ is Val and X⁴ is Leu, X³ is Val and X⁴ is Ile, X³ is Val and X⁵ is Ser, X³ is Val and X⁵ is Met, X³ is Val and X⁶ is Leu, X³ is Val and X⁶ is Val, X³ is Val and X⁶ is Ala, X³ is Gly and X⁴ is Leu, X³ is Gly and X⁴ is Ile, X³ is Gly and X⁵ is Ser, X³ is Gly and X⁵ is Met, X³ is Gly and X⁶ is Leu, X³ is Gly and X⁶ is Val, X³ is Gly and X⁶ is Ala, X³ is Ile and X⁴ is Leu, X³ is Ile and X⁴ is Ile, X³ is Ile and X⁵ is Ser, X³ is Ile and X⁵ is Met, X³ is Ile and X⁶ is Leu, X³ is Ile and X⁶ is Val, X³ is Ile and X⁶ is Ala, X⁴ is Leu and X⁵ is Ser, X⁴ is Leu and X⁵ is Met, X⁴ is Leu and X⁶ is Leu, X⁴ is Leu and X⁶ is Val, X⁴ is Leu and X⁶ is Ala, X⁴ is Ile and X⁵ is Ser, X⁴ is Ile and X⁵ is Met, X⁴ is Ile and X⁶ is Leu, X⁴ is Ile and X⁶ is Val, X⁴ is Ile and X⁶ is Ala, X⁵ is Ser and X⁶ is Leu, X⁵ is Ser and X⁶ is Val, X⁵ is Ser and X⁶ is Ala, X⁵ is Met and X⁶ is Leu, X⁵ is Met and X⁶ is Val, and X⁵ is Met and X⁶ is Ala.

In certain embodiments, the peptide may comprise a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-X-Met-Val-Leu-Ile-Ser-Leu  (Formula II)

-   -   wherein X is any amino acid.

In some such embodiments, X is Ser (S) or Asp (D). As such, in some embodiments, X is Ser (S) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVSMVLISL. In some embodiments, X is Asp (D) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVDMVLISL.

In certain cases, the method may comprise contacting a T cell obtained from a subject having Neuromyelitis Optica with (i) a peptide comprising an amino acid sequence having at least 60% sequence identity to the amino acid sequence of a human Aquaphorin-4 (AQP-4) peptide: LPVDMVLISL wherein the peptide is up to 50 amino acids in length, and (ii) a candidate agent and evaluating the number of T cells, wherein a decrease in the number of T cells as compared to a control indicates that the candidate agent inhibits proliferation of T cells.

Candidate agents of interest for screening include biologically active agents of numerous chemical classes, organic molecules, inorganic molecules, organometallic molecules, immunoglobulins, peptides, proteins, genetic sequences, etc. Also of interest are small organic molecules, which comprise functional groups necessary for structural interaction with proteins, particularly hydrogen bonding, and typically include at least an amine, carbonyl, hydroxyl or carboxyl group, frequently at least two of the functional chemical groups. The candidate agents often comprise cyclical carbon or heterocyclic structures and/or aromatic or polyaromatic structures substituted with one or more of the above functional groups. Candidate agents are also found among biomolecules, including peptides, polynucleotides, saccharides, fatty acids, steroids, purines, pyrimidines, derivatives, structural analogs or combinations thereof.

Candidate agents may be compounds. Compounds may be obtained from a wide variety of sources including libraries of synthetic or natural compounds. For example, numerous means are available for random and directed synthesis of a wide variety of organic compounds, including biomolecules, including expression of randomized oligonucleotides and oligopeptides. Alternatively, libraries of natural compounds in the form of bacterial, fungal, plant and animal extracts are available or readily produced. Additionally, natural or synthetically produced libraries and compounds are readily modified through conventional chemical, physical and biochemical means, and may be used to produce combinatorial libraries. Known pharmacological agents may be subjected to directed or random chemical modifications, such as acylation, alkylation, esterification, amidification, etc., to produce structural analogs.

A plurality of assays may be run in parallel with different concentrations to obtain a differential response to the various concentrations. As known in the art, determining the effective concentration of an agent typically uses a range of concentrations resulting from 1:10, or other log scale, dilutions. The concentrations may be further refined with a second series of dilutions, if necessary. Typically, one of these concentrations serves as a negative control, i.e. at zero concentration or below the level of detection of the agent or at or below the concentration of agent that does not give a detectable change in binding.

A candidate agent is identified as an inhibitor of AQP-4 specific T cell proliferation if it decreases AQP-4 specific T cell proliferation by at least about 5%, or at least about 10%, or at least about 20%, or at least about 50%, or at least about 70%, or at least about 80%, or at least about 90%, or more, compared to AQP-4 specific T cell proliferation in absence of the candidate agent, or another negative control.

A T cell obtained from a NMO patient used in the screening method, may be present in a blood sample from the NMO patient, or present in a purified form, such as, isolated from the blood sample. The contacting with a peptide as provided herein and a candidate agent may be simultaneous or sequential. The contacting may be performed for 1 day, or 5 days, or 10 days, or 15 days, or 20 days, or 25 days, or 30 days. T cell proliferation may be evaluated by methods known in the art.

Induction of Immune Tolerance to AQP4

A method for inducing immune tolerance to AQP-4 protein and fragments thereof in a subject is also provided. As such, the peptides disclosed herein may be used in a tolerizing therapy to suppress immune response to AQP-4 protein and fragments thereof. In general, the method comprises administering an effective dose of a peptide to a subject, wherein the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-X¹-X²-Met-X³-X⁴-Ile-X⁵-X⁶  (Formula I)

wherein X¹, X², X³, X⁴, X⁵, and X⁶ are any amino acid,

wherein the peptide is up to 50 amino acids in length, and

wherein the administering the peptide induces immune tolerance to AQP-4 protein and fragments thereof in the subject.

In certain embodiments, X¹ is Val (V) or Ile (I). In certain embodiments, X² is Ser (S) or Asp (D). In certain embodiments, X³ is Val (V), Ile (I), or Gly (G). In certain embodiments, X⁴ is Leu (L) or Ile (I). In certain embodiments, X⁵ is Met (M) or Ser (S). In certain embodiments, X⁶ is Leu (L), Val (V), or Ala (A). In certain embodiments, X¹ is Val (V), X² is Ser (S) or Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L).

In certain embodiments, X¹ is Val (V), X² is Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Asp-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Val (V). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: Leu-Pro-Val-Ser-Met-Gly-Leu-Ile-Ser-Val.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Ile (I), X⁴ is Ile (I), X⁵ is Met (M), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Ile-Ile-Ile-Met-Leu.

In certain embodiments, X¹ is Ile (I), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Ala (A). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Ile-Ser-Met-Gly-Leu-Ile-Ser-Ala.

Examples of suitable embodiments include where:

X¹ is Val and X² is Ser, X¹ is Val and X² is Asp, X¹ is Val and X³ is Val, X¹ is Val and X³ is Gly, X¹ is Val and X³ is Ile, X¹ is Val and X⁴ is Leu, X¹ is Val and X⁴ is Ile, X¹ is Val and X⁵ is Ser, X¹ is Val and X⁵ is Met, X¹ is Val and X⁶ is Leu, X¹ is Val and X⁶ is Val, X¹ is Val and X⁶ is Ala, X¹ is Ile and X² is Ser, X¹ is Ile and X² is Asp, X¹ is Ile and X³ is Val, X¹ is Ile and X³ is Gly, X¹ is Ile and X³ is Ile, X¹ is Ile and X⁴ is Leu, X¹ is Ile and X⁴ is Ile, X¹ is Ile and X⁵ is Ser, X¹ is Ile and X⁵ is Met, X¹ is Ile and X⁶ is Leu, X¹ is Ile and X⁶ is Val, X¹ is Ile and X⁶ is Ala, X² is Ser and X³ is Val, X² is Ser and X³ is Gly, X² is Ser and X³ is Ile, X² is Ser and X⁴ is Leu, X² is Ser and X⁴ is Ile, X² is Ser and X⁵ is Ser, X² is Ser and X⁵ is Met, X² is Ser and X⁶ is Leu, X² is Ser and X⁶ is Val, X² is Ser and X⁶ is Ala, X² is Asp and X³ is Val, X² is Asp and X³ is Gly, X² is Asp and X³ is Ile, X² is Asp and X⁴ is Leu, X² is Asp and X⁴ is Ile, X² is Asp and X⁵ is Ser, X² is Asp and X⁵ is Met, X² is Asp and X⁶ is Leu, X² is Asp and X⁶ is Val, X² is Asp and X⁶ is Ala, X³ is Val and X⁴ is Leu, X³ is Val and X⁴ is Ile, X³ is Val and X⁵ is Ser, X³ is Val and X⁵ is Met, X³ is Val and X⁶ is Leu, X³ is Val and X⁶ is Val, X³ is Val and X⁶ is Ala, X³ is Gly and X⁴ is Leu, X³ is Gly and X⁴ is Ile, X³ is Gly and X⁵ is Ser, X³ is Gly and X⁵ is Met, X³ is Gly and X⁶ is Leu, X³ is Gly and X⁶ is Val, X³ is Gly and X⁶ is Ala, X³ is Ile and X⁴ is Leu, X³ is Ile and X⁴ is Ile, X³ is Ile and X⁵ is Ser, X³ is Ile and X⁵ is Met, X³ is Ile and X⁶ is Leu, X³ is Ile and X⁶ is Val, X³ is Ile and X⁶ is Ala, X⁴ is Leu and X⁵ is Ser, X⁴ is Leu and X⁵ is Met, X⁴ is Leu and X⁶ is Leu, X⁴ is Leu and X⁶ is Val, X⁴ is Leu and X⁶ is Ala, X⁴ is Ile and X⁵ is Ser, X⁴ is Ile and X⁵ is Met, X⁴ is Ile and X⁶ is Leu, X⁴ is Ile and X⁶ is Val, X⁴ is Ile and X⁶ is Ala, X⁵ is Ser and X⁶ is Leu, X⁵ is Ser and X⁶ is Val, X⁵ is Ser and X⁶ is Ala, X⁵ is Met and X⁶ is Leu, X⁵ is Met and X⁶ is Val, and X⁵ is Met and X⁶ is Ala.

In certain embodiments, the peptide may comprise a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-X-Met-Val-Leu-Ile-Ser-Leu  (Formula II)

wherein X is any amino acid.

In some such embodiments, X is Ser (S) or Asp (D). As such, in some embodiments, X is Ser (S) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVSMVLISL. In some embodiments, X is Asp (D) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVDMVLISL.

In certain embodiments, the peptide may comprise an amino acid sequence having at least 60% sequence identity to the amino acid sequence of a human Aquaphorin-4 (AQP-4) peptide having the amino acid sequence: LPVDMVLISL wherein the peptide is up to 50 amino acids in length, wherein the administering the peptide induces immune tolerance to AQP-4 protein and fragments thereof in the subject. The phrase “fragments of AQP-4 protein” as used in the context of AQP4 fragments that do not induce an immune reaction in a subject treated with the peptides disclosed herein refer to AQP4 fragments comprising an amino acid sequence homologous to the amino acid sequence of the peptide used for induction of immune tolerance. For example, the AQP4 fragments may include a stretch of amino acids having: the consensus sequence Leu-Pro-Val-X-Met-Val-Leu-Ile-Ser-Leu, or having at least 60% sequence identity to the sequence: LPVDMVLISL

In certain embodiments, the subject may be predisposed or at risk of developing NMO. In certain embodiments, the subject may have been diagnosed with NMO.

The peptide(s) may be administered to an individual as a pharmaceutically acceptable composition. Pharmaceutically acceptable peptide compositions for administering to an individual may include, for example, sterile aqueous or non-aqueous solutions, suspensions, and emulsions. Examples of components, such as, carriers, present in pharmaceutically acceptable peptide compositions include, without limitation, propylene glycol, polyethylene glycol, vegetable oils, and injectable organic esters. Aqueous carriers include water, alcohol, saline, and buffered solutions. Pharmaceutically acceptable carriers can also include physiologically acceptable aqueous vehicles (e.g., physiological saline or artificial cerebral-spinal fluid) or other known carriers appropriate to specific routes of administration. Additional compounds can be included with the peptide(s) described herein, such as steroids, mucolytic agents, anti-inflammatory agents, immunosuppressants, dilators, vasoconstrictors, or combinations thereof. Preservatives, flavorings, and other additives such as, for example, anti-microbials, anti-oxidants, chelating agents, inert gases, and the like may also be present.

In certain cases, the peptide(s) may be administered at an amount that is sufficient to suppress induction of an immune response to AQP4 or fragments thereof. In certain cases, the amount may be sufficient to suppress production of AQP4 specific antibodies in the subject. In certain cases, the amount may be sufficient to suppress production of AQP4 specific T cells in the subject. In certain cases, the amount may be sufficient to suppress production of AQP4 specific T cells and antibodies in the subject. In certain embodiments, a subject receiving the AQP4 tolerizing therapy as described above, may show a 5%-90% decrease in the titer of AQP4 specific antibodies present in the subject as compared the titer of the antibodies present before the therapy. In certain embodiments, a subject receiving the AQP4 tolerizing therapy as described above, may show a 5%-90% decrease in the number of AQP4 specific T cells present in the subject as compared the number of AQP4 specific T cells present before the therapy. In certain cases, the AQP4 tolerizing therapy may result in a substantial decrease (e.g., 5%-90% decrease) in the number of Th17 cells present in the subject as compared the number present before the therapy.

In certain cases, the peptide may be administered at a high dose, such as, 0.1-10 mg/Kg, such as, 0.1 mg/Kg, 0.3 mg/Kg, 1 mg/Kg, 3 mg/Kg, or 10 mg/Kg.

In certain cases, the peptide may be administered to the thymus of the subject. In certain cases, the peptide may be orally administered to the subject. In certain cases, the method may include repeated administration of the peptide, such as, every 10 days, 20 days, 30 days, 3 months, 6 months, 12 months, 3 years, 6 years, 10 years, and so forth. In certain cases, the initial dose of the peptide may be higher than the dose of the peptide in subsequent administration to the subject.

Kits

Kits including the peptides described herein are disclosed. Kits may include one or more peptides comprising a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-X¹-X²-Met-X³-X⁴-Ile-X⁵-X⁶  (Formula I)

wherein X¹, X², X³, X⁴, X⁵, and X⁶ are any amino acid, and

wherein the peptide is up to 50 amino acids in length.

In certain embodiments, X¹ is Val (V) or Ile (I). In certain embodiments, X² is Ser (S) or Asp (D). In certain embodiments, X³ is Val (V), Ile (I), or Gly (G). In certain embodiments, X⁴ is Leu (L) or Ile (I). In certain embodiments, X⁵ is Met (M) or Ser (S). In certain embodiments, X⁶ is Leu (L), Val (V), or Ala (A). In certain embodiments, X¹ is Val (V), X² is Ser (S) or Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L).

In certain embodiments, X¹ is Val (V), X² is Asp (D), X³ is Val (V), X⁴ is Leu

(L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Asp-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Val-Leu-Ile-Ser-Leu.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Val (V). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Gly-Leu-Ile-Ser-Val.

In certain embodiments, X¹ is Val (V), X² is Ser (S), X³ is Ile (I), X⁴ is Ile (I), X⁵ is Met (M), and X⁶ is Leu (L). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-Ser-Met-Ile-Ile-Ile-Met-Leu.

In certain embodiments, X¹ is Ile (I), X² is Ser (S), X³ is Gly (G), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Ala (A). In such embodiments, the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Ile-Ser-Met-Gly-Leu-Ile-Ser-Ala.

Examples of suitable embodiments include where:

X¹ is Val and X² is Ser, X¹ is Val and X² is Asp, X¹ is Val and X³ is Val, X¹ is Val and X³ is Gly, X¹ is Val and X³ is Ile, X¹ is Val and X⁴ is Leu, X¹ is Val and X⁴ is Ile, X¹ is Val and X⁵ is Ser, X¹ is Val and X⁵ is Met, X¹ is Val and X⁶ is Leu, X¹ is Val and X⁶ is Val, X¹ is Val and X⁶ is Ala, X¹ is Ile and X² is Ser, X¹ is Ile and X² is Asp, X¹ is Ile and X³ is Val, X¹ is Ile and X³ is Gly, X¹ is Ile and X³ is Ile, X¹ is Ile and X⁴ is Leu, X¹ is Ile and X⁴ is Ile, X¹ is Ile and X⁵ is Ser, X¹ is Ile and X⁵ is Met, X¹ is Ile and X⁶ is Leu, X¹ is Ile and X⁶ is Val, X¹ is Ile and X⁶ is Ala, X² is Ser and X³ is Val, X² is Ser and X³ is Gly, X² is Ser and X³ is Ile, X² is Ser and X⁴ is Leu, X² is Ser and X⁴ is Ile, X² is Ser and X⁵ is Ser, X² is Ser and X⁵ is Met, X² is Ser and X⁶ is Leu, X² is Ser and X⁶ is Val, X² is Ser and X⁶ is Ala, X² is Asp and X³ is Val, X² is Asp and X³ is Gly, X² is Asp and X³ is Ile, X² is Asp and X⁴ is Leu, X² is Asp and X⁴ is Ile, X² is Asp and X⁵ is Ser, X² is Asp and X⁵ is Met, X² is Asp and X⁶ is Leu, X² is Asp and X⁶ is Val, X² is Asp and X⁶ is Ala, X³ is Val and X⁴ is Leu, X³ is Val and X⁴ is Ile, X³ is Val and X⁵ is Ser, X³ is Val and X⁵ is Met, X³ is Val and X⁶ is Leu, X³ is Val and X⁶ is Val, X³ is Val and X⁶ is Ala, X³ is Gly and X⁴ is Leu, X³ is Gly and X⁴ is Ile, X³ is Gly and X⁵ is Ser, X³ is Gly and X⁵ is Met, X³ is Gly and X⁶ is Leu, X³ is Gly and X⁶ is Val, X³ is Gly and X⁶ is Ala, X³ is Ile and X⁴ is Leu, X³ is Ile and X⁴ is Ile, X³ is Ile and X⁵ is Ser, X³ is Ile and X⁵ is Met, X³ is Ile and X⁶ is Leu, X³ is Ile and X⁶ is Val, X³ is Ile and X⁶ is Ala, X⁴ is Leu and X⁵ is Ser, X⁴ is Leu and X⁵ is Met, X⁴ is Leu and X⁶ is Leu, X⁴ is Leu and X⁶ is Val, X⁴ is Leu and X⁶ is Ala, X⁴ is Ile and X⁵ is Ser, X⁴ is Ile and X⁵ is Met, X⁴ is Ile and X⁶ is Leu, X⁴ is Ile and

X⁶ is Val, X⁴ is Ile and X⁶ is Ala, X⁵ is Ser and X⁶ is Leu, X⁵ is Ser and X⁶ is Val, X⁵ is Ser and X⁶ is Ala, X⁵ is Met and X⁶ is Leu, X⁵ is Met and X⁶ is Val, and X⁵ is Met and X⁶ is Ala.

In certain embodiments, the peptide may comprise a contiguous stretch of amino acids having the consensus amino acid sequence:

Leu-Pro-Val-X-Met-Val-Leu-Ile-Ser-Leu  (Formula II)

wherein X is any amino acid.

In some such embodiments, X is Ser (S) or Asp (D). As such, in some embodiments, X is Ser (S) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVSMVLISL. In some embodiments, X is Asp (D) and the peptide comprises a contiguous stretch of amino acids having the consensus amino acid sequence: LPVDMVLISL.

In certain cases, the kits may include a peptide(s) having at least 60% sequence identity to the amino acid sequence of a human Aquaphorin-4 (AQP-4) peptide having the amino acid sequence: LPVDMVLISL, wherein the peptide is up to 50 amino acids in length. The kit may contain the peptide(s) in a solid, semi-solid, liquid, or fluid state. The kit may include one or multiple containers containing specified quantities of the peptide(s). In certain embodiments, the kit may include multiple containers containing the subject peptides described herein unit dosage form.

In certain embodiments, the kit may further include reagents and instructions for carrying out diagnosing, treating, or screening methods using the peptides.

EXAMPLES

The following example is provided to further illustrate the advantages and features of the present invention, but is not intended to limit the scope of the invention. While they are typical of those that might be used, other procedures, methodologies, or techniques known to those skilled in the art may alternatively be used.

Materials and Methods

Patients.

Fifteen NMO patients (12 females and 3 males, 44.3+/−13.8 years) fulfilling Mayo Clinic diagnostic criteria (Wingerchuk D M, et al., Neurology. 2006 May 23; 66(10):1485-9) and nine HC (5 females and 4 males, 40.8+/−10.7 years) were recruited from the UCSF MS Center. A majority of NMO patients had been treated with rituximab (Jacob A, et al., Arch Neurol. 2008 November; 65(11):1443-8), and none had been treated with azathioprine, mycophenolate mofetil, cyclophosphamide or other immunosuppressive medications. None of the patients had received steroids within two months preceding blood draws. Blood was collected by venipuncture. This study was approved by UCSF Committee on Human Research (Protocol #10-00650) and written informed consent was obtained from subjects prior to enrollment.

T Cell Proliferation Assays.

Peripheral blood mononuclear cells (PBMC) were isolated by density gradient centrifugation over Ficoll (Ficoll-Paque PLUS, GE Healthcare) according to manufacturer's instruction. T cell proliferation was evaluated by [³H] thymidine incorporation or CFSE dilution assays. In thymidine incorporation assays, PBMC were cultured with antigens in 96-well plates at either 1×10⁵ cells (AQP4 pools—in at least 10 wells) or 5×10⁵ cells (individual peptides—in duplicate) per well for 6 days (d). Cultures were then pulsed with [³H] thymidine and harvested 18 h later. Positive wells were defined as having counts-per-minute (cpm) values greater than control cpm average values+3 standard deviation (SD) or stimulation index (SI) greater than 2. Alternatively, PBMC were stained with 1 μM CFSE (Invitrogen), according to manufacturer's instruction. Cells were cultured in the presence of antigens for 10 d. T cell proliferation was assessed by flow cytometric evaluation of CFSE dilution. Proliferation was expressed as the cell division index (CDI) (defined as the number of CFSE^(low) T cells cultured with antigen/number of CFSE^(low) T cells without antigen). In all cases, culture medium consisted of X-VIVO 15 (Lonza) supplemented with penicillin (100 U/ml) and streptomycin (0.1 mg/ml).

Antigens.

Peptides were synthesized by Genemed Synthesis Inc. with purity greater than 95% by HPLC analysis. Overlapping AQP4 20-mer peptides were offset by 10 amino acids. Peptides corresponding to certain hydrophobic AQP4 sequences were synthesized in overlapping 15-mer peptide pairs. Truncated peptides within the 61-80 region (p61-78 GTEKPLPVDMVLISLCFG; p61-76 GTEKPLPVDMVLISLC; p61-74 GTEKPLPVDMVLIS; p61-72 GTEKPLPVDMVL; p63-80 EKPLPVDMVLISLCFGLS; p65-80 PLPVDMVLISLCFGLS; p67-80 PVDMVLISLCFGLS; p69-80 DMVLISLCFGLS), AQP4 p63-76 (EKPLPVDMVLISLC) and bacterial peptide ABC/TP p204-217 (FIILPVSMVLISLV) were as quoted. Full length recombinant human (rh) AQP4 (1-323) was expressed in Pichia pastoris and purified as described (Ho J D, et al., Proc Natl Acad Sci USA. 2009 May 5; 106(18):7437-42). Tetanus toxoid was obtained from List Biological Laboratories, Inc. (Campbell, Calif.).

Flow Cytometry Analysis.

Single-cell suspensions were incubated with human serum to prevent nonspecific antibody binding, then stained with anti-CD3, -CD4, -CD8, CD25, -MHC Class II, -CD40, -CD80, and -CD86 (eBioscience and BD Bioscience). Intracellular cytokine production by CD4 T cells and APC was analyzed by monitoring the expression of IFN-γ, IL-17, IL-6, IL-10 and IL-10 (1:100) (eBioscience). Foxp3 staining was performed according to the manufacturer's protocol (eBioscience). For intracellular cytokine staining, T cells were stimulated with phorbol 12-myristate 13-acetate (PMA, 50 ng/ml) plus ionomycin (500 ng/ml) in the presence of GolgiStop (1 μl/ml) (BD Biosciences). CD14 cells were stimulated with LPS (1 μg/ml; Sigma-Aldrich) for 4 or 20 h in the presence of GolgiStop. Cells were analyzed by flow cytometry on a FACS Canto flow cytometer (BD Biosciences).

Blocking of HLA Alleles with Antibodies.

Inhibition of the proliferation of PBMC to AQP4 p61-80 and rhAQP4 was studied by using mouse monoclonal anti-HLA-DR (clone G46-6; BD Bioscience, Mississauga, ON, Canada), anti-HLA-DQ (clone HG-38; Abcam), anti-HLA-DP (clone B7/21; Abcam) and isotype control (clone G155-178; BD Biosciences). Antibodies (1 μg/ml) were added to CFSE-stained PBMC cultures 1 hour before addition of antigens.

Antigen Recall Experiments.

PBMC were initially stimulated with antigens. After 10 d, cells were restimulated with rhAQP4 (5 μg/ml), AQP4 peptides or bacterial peptide

(10 μg/ml), in the presence of irradiated autologous APC. Following 3 d of stimulation, cultures were pulsed with [³H]thymidine and harvested 18 h later. Stimulation Index (SI) was calculated by dividing cpm in wells with antigen by cpm in control wells with no antigen of each assay test group.

Analyses for Protein Sequence Homology and MHC Core Binding Motifs.

Sequences similarities between AQP4 and other proteins were addressed using the protein-protein Basic Local Alignment Search Tool (BLAST) from NCBI. The prediction of the core binding motif within AQP4 61-80 sequence for HLA-DRB1*0301 and HLA-DRB3*0202 was performed with netMHCII-1.1 (Nielsen M, et al., BMC Bioinformatics. 2007; 8:238) and net MHCII-2.2 (Nielsen M, et al., BMC Bioinformatics. 2009; 10:296), programs that utilizes relative affinities of identified determinants from the immune epitope database (IEDB).

HLA Typing.

High-resolution HLA typing was performed by the UCSF

Immunogenetics and Transplantation Laboratory (ITL, UCSF Department of Surgery). The following HLA loci were analyzed using sequence-based typing: DRB1, DRB3/4/5, DQA1, DQB1, DPA1, and DPB1. Sequence ambiguities outside exon 2 were resolved.

Statistics.

Statistical analysis was performed using either GraphPad Prism software or STATA. The nonparametric Mann-Whitney U test was used to compare data. Paired t-tests were performed to compare cpm values with antigens to control values with no antigens presented in FIG. 3E. A value of P<0.05 was considered significant.

Example 1 T Cells from NMO Patients Recognize Discrete AQP4 Determinants and are Restricted by HLA-DR Molecules

In general, antigen-specific T cells recognize linear peptide fragments of 10-15 amino acids in association with MHC(HLA) proteins expressed on APC (Zamvil S S, et al., Nature. 1986 Nov. 20-26; 324(6094):258-60). In order to identify AQP4-specific T cells in NMO patients, proliferation of peripheral blood mononuclear cells (PBMC) to a library of 32 synthetic overlapping 15mer and 20mer peptides encompassing the 323 amino acid sequence of full-length human AQP4 (M1 isoform) was initially tested. Here, separate pools containing five overlapping AQP4 peptides were studied. By [³H]thymidine incorporation, more frequent proliferative responses in primary cultures to AQP4 pools 1-55, 46-100, 126-170, 201-250 and 241-300 was detected (FIG. 1A). Lymphocytes from healthy controls (HC) also proliferated to some of these pools, and exhibited comparable responses to tetanus toxoid (TT).

Having identified candidate regions of AQP4 containing T cell determinants, proliferative responses of NMO patients to individual AQP4 peptides was then tested. T cell determinants were identified within peptides (p) 21-40, 61-80, 131-150, 156-170 and 211-230 (FIG. 1B), which corresponded to intracellular, extracellular and transmembrane sequences of AQP4 (FIG. 1C). Interestingly, three of these AQP4 determinants, p61-80, p131-150 and p211-230, respectively, are located in extracellular A, C and E loops, AQP4 domains targeted by NMO-IgG (Owens G, et al., Mult Scler. 2011; 17(10 Suppl):5291-52). The fluorescent dye 5,6-caroxylfluorescein diacetate succinimidyl ester (CFSE) dilution assay is considered a more powerful and sensitive method for detecting proliferation of rare autoantigen-specific human T cells than the traditional [³H]thymidine incorporation (Mannering S I, et al., J Immunol Methods. 2003 December; 283(1-2):173-83). Using this approach, responses to individual AQP4 peptides identified in the initial screening, and also to AQP4 T cell determinants common to mouse strains with distinct MHC haplotypes was examined (Nelson P A, et al., PLoS One. 2010 November 2010; 5(11):e15050 1-9; Kalluri S R, et al., PLoS ONE. 2011; 6(1):e16083). A robust proliferative T cell response to p61-80, which is located within the extracellular A loop, was detected in all NMO patients tested. T cell responses were observed to AQP4 p21-40, p156-170, p11-30 and p261-280 (FIG. 1D), even though substantial proliferation to the latter two peptides in the initial [³H]thymidine incorporation assays was not detected. T cells from HC also recognized these AQP4 peptides, but again, the proliferative responses were both lower and less frequent than in NMO patients. Proliferating AQP4-specific T cells were predominantly CD4 and the proportion of CD4 T cells that responded to AQP4 p61-80 was higher in NMO patients than HC (FIG. 1E).

Presentation of native protein antigens by APC generally requires proteolytic processing (Slavin A J, et al., J Clin Invest. 2001; 108(8):1133-9; Soos J M, et al., J. Immunol. 1998 Dec. 1; 161(11):5959-66; Zamvil S, et al., Nature. 1985 Sep. 26-Oct. 2; 317(6035):355-8; Vyas J M, et al., Nat Rev Immunol. 2008 August; 8(8):607-18.). Therefore, it was examined whether the identified AQP4 peptides contained natural T cell determinants of intact AQP4. When T cells initially stimulated with rhAQP4 were tested for recall responses to individual AQP4 peptides, proliferation to AQP4 p21-40 and p61-80 was observed, indicating that these are naturally processed determinants of AQP4 (FIG. 1F). Among peptides that were examined, AQP4 p61-80 was clearly immunodominant. Several studies have identified over-representation of HLA-DPB1*0501, HLA-DRB1*0301 or HLA-DRB3 in NMO patients (Matsushita T, et al., Tissue Antigens. 2009 February; 73(2):171-6; Brum D G, et al., Mult Scler. 2010 January; 16(1):21-9; Deschamps R, et al., Mult Scler. 2011 January; 17(1):24-31), suggesting these MHC II alleles could serve as restriction elements for CD4 T cells in NMO. A high representation of these HLA alleles in the patient cohort was also identified, in particular, an overrepresentation of HLA-DRB3*0202 among NMO subjects was noted (Table 2).

TABLE 2 HLA haplotypes of NMO patients and healthy controls DRB1*1501^(a) DQB1*0602^(a) DRB1*0301^(b) DRB3*0202^(b) DPB1*0501^(b) NMO  3/15  2/15  7/15 11/15  7/15 Patients 20%   13%   47%   73%   47% Healthy 2/8 1/8 3/8 3/8 3/8 Controls 25% 12.5% 37.5% 37.5% 37.5% ^(a)Alleles associated with multiple sclerosis susceptibility; ^(b)Alleles associated with neuromyelitis optica susceptibility

Using MHC II blocking antibodies, it was observed that T cell proliferative responses to AQP4 p61-80 were inhibited by anti-HLA-DR, but were not statistically inhibited by anti-HLA-DQ or anti-HLA-DP, demonstrating that HLA-DR molecules serve as restriction elements for T cells that recognize this determinant (FIG. 2A). Proliferation of AQP4 p61-80-specific T cells from HLA-matched HC (Table 2) was also inhibited by anti-HLA-DR antibodies (FIG. 2B). Further, a similar MHC II-restriction profile was observed after stimulating T cells from NMO patients with rhAQP4 (FIG. 2C) suggesting that other AQP4 determinants may also be restricted by HLA-DR molecules.

FIGS. 1A-1F. T cells from NMO patients recognize discrete determinants of AQP4. PBMC were tested for proliferation to (Panel A) pools of AQP4 peptides (n=8 NMO and n=3 HC) and to (Panel B) individual AQP4 peptides identified from those pools. In (Panel A and Panel B) PBMC were cultured for 6 d in the presence of AQP4 pools (10 μg/ml) or AQP4 peptides (10 μg/ml), respectively, then pulsed with [³H]thymidine and harvested 18 h later. In (Panel A), positive wells were defined as values>control cpm average values+3SD. (Panel C) AQP4 determinants are represented within a human AQP4 topological diagram using Johns S J, TOPO2, Transmembrane protein display software (Crane J M, et al., Neuroscience. 2010 Jul. 28; 168(4):892-902.). (Panel D and Panel E) PBMC were examined by CFSE dilution for proliferation to individual AQP4 peptides (10 μg/ml), rhAQP4 (5 μg/ml) or in (Panel E) tetanus toxoid (TT) (1 μg/ml) after 10 d of culture. CFSE was measured in CD3 CD4 and CD8⁺ T cells by FACS and quantified by cell division index (CDI). CDI>2 (broken lines) was considered positive. (Panel F) Recall T cell proliferation ([³H]thymidine incorporation) to individual AQP4 peptides (10 μg/ml) or rhAQP4 (5 μg/ml) was detected after initial stimulation with rhAQP4 (5 μg/ml) for 10 d. In Panels A and E, error bars indicate SEM; in B, D and F, horizontal lines indicate mean values. *P<0.05 Mann-Whitney U test.

FIG. 2A-2C. HLA-DR serves as a restriction element for AQP4-specific T cells. (Panels A and B) CFSE-labeled PBMC from NMO patients were cultured for 10 d with antigens alone or in combination with anti-HLA-DR, -HLA-DQ, -HLA-DP or isotype control antibodies. T cell proliferation was evaluated by FACS analysis of CFSE dilution. Inhibitory effects of blocking antibodies were examined on proliferating CD4 T cells (n=7 NMO in (Panel A) and n=4 NMO in (Panel B)). T cell proliferation is expressed as cell division index (CDI). (Panel C) PBMC from HC were similarly examined after stimulation with AQP4 p61-80 (n=2). Error bars represent SEM. *P<0.05, Mann-Whitney U test.

Example 2 AQP4 P63-76-Specific T Cells Cross-React with C. perfringens ABC Transporter Permease P204-217

In order to characterize the fine specificity of AQP4 p61-80-specific T cells, proliferation to truncated peptides corresponding to sequences within this region was examined. AQP4 p61-80-specific T cells proliferated in response to p61-78 and p61-76 but not to p61-74 or p61-72 (FIG. 3A). Shorter AQP4 peptides truncated from the N-terminal sequence, p65-80, p67-80 and p69-80 also stimulated proliferation of p61-80-specific T cells although less efficiently than p63-80. Collectively, these findings indicated that p63-76 contained the core determinant of AQP4 61-80. In this regard, it was observed that p61-80-specific T cells responded nearly as efficiently to p63-76 as to p61-80 (FIG. 3B). Interesting, AQP4 63-76 contains the predicted binding motif for HLA-DRB1*0301 and HLA-DRB3*0202 (FIG. 3C).

Immune responses to pathogens may elicit cross-reactivity to self-antigens that share structural or sequence homology (Fujinami R S, Oldstone M B. Science. 1985 Nov. 29; 230(4729):1043-5; Wucherpfennig K W, Strominger J L. Cell. 1995 Mar. 10; 80(5):695-705). This process, known as ‘molecular mimicry’, is considered one important potential mechanism in autoimmunity. Having found that p63-76 contains an immunodominant AQP4 T cell epitope, whether this sequence might share homology with other proteins was addressed. 90% homology between AQP4 66-75 and the ten amino acid sequence 207-216 within conserved ABC transporter permease (ABC-TP) proteins from several strains of the bacterium Clostridium perfringens (NCBI protein reference sequences ZP_(—)02952885.1, ZP_(—)02638213.1, ZP_(—)02634520.1, ZP_(—)02630305.1; 90% positives, 90% identities, 0% gaps) was identified (FIG. 3C). T cells from NMO patients proliferated significantly to ABC-TP p204-217, although less intensely than to AQP4 p61-80 and AQP4 p63-76 (FIG. 3D). To directly test for cross-reactivity, T cells initially stimulated with AQP4 p63-76 or ABC-TP were tested for recall responses in a reciprocal manner (FIG. 3E). Importantly, AQP4-primed T cells proliferated to ABC-TP p204-217 and vice versa, supporting molecular mimicry between this bacterial transmembrane protein and AQP4. Confirming specificity of those recall responses, proliferation to p156-170 was not observed.

FIG. 3A-3E. Cross-reactivity between AQP4 p63-76 and Clostridium perfringens ABC transporter permease (ABC/TP) p204-217. (Panel A) The T cell epitope within AQP4 p61-80 was mapped by testing recall proliferation of AQP4 p61-80-reactive T cells from NMO patients to truncated AQP4 peptides (10 μg/ml) in the presence of irradiated autologous APC. (Panel B) AQP4 p63-76 appeared to contain p61-80 core determinant. Proliferation was measured by [³H]thymidine incorporation after 3 d. Data are representative of three independent experiments. (Panel C) Sequence homology between AQP4 p63-76 and C. perfringens ABC transporter permease (ABC-TP) p204-217 was identified using the protein-protein Basic Local Alignment Search Tool (BLAST) from NCBI. Top bracket represents the predicted core binding motif for HLA-DRB1*0301 and HLA-DRB3*0202 within AQP4 p63-76 (netMHCII-1.1 and -2.2 programs). (Panel D) CFSE-labeled PBMC from 3 NMO patients were stimulated with antigens (10 μg/ml) and cultured for 10 d before evaluating proliferation by FACS. (Panel E) PBMC from 4 NMO patients were initially stimulated for 10 d with AQP4 p63-76 or ABC/TP p204-217 at 10 μg/ml. Recall responses to peptides in the presence of irradiated autologous APC were evaluated by [³H]thymidine incorporation after 3 d. Paired t-tests were performed to compare counts per minute (cpm) values of each antigen to cpm values of no-antigen controls, *P<0.05, **P<0.01. In (Panel A), (Panel B) and (Panel E) data are presented as means of duplicate or triplicate wells; in (Panels A-E) error bars indicate SEM.

Example 3 AQP4 P61-80-Specific T Cells from NMO Patients Exhibit Pro-Inflammatory Th17 Polarization

Although indirect, some clinical and histologic data suggest Th17 cells may participate in NMO pathogenesis (Lucchinetti C F, et al. Brain. 2002 July; 125(Pt 7):1450-61; Warabi Y, et al., J Neurol Sci. 2006 Nov. 15; 249(2):145-52). Thus, proinflammatory cytokine production in proliferating AQP4-specific T cells was examined. In comparison to HC, significantly higher frequencies of IL-17⁺ single- and IL-17⁺IFN-γ⁺ double-positive cells that recognized p61-80 in NMO patients was observed (FIGS. 4A, B). An increased frequency of Th17 cells from NMO patients was observed after stimulation with rhAQP4, but was not significant. No Th17 bias was detected in response to AQP4 p156-170, suggesting the Th17 polarization may be epitope-specific. In contrast, IFN-γ production by AQP4-specific T cells appeared unchanged between the two groups. Thus, the Th17/Th1 ratio was elevated in NMO patients in response to the immunodominant determinant AQP4 p61-80, but not to the other antigens tested. Interestingly, a difference in the frequency of peripheral blood regulatory T cells (Treg) from NMO patients and HC was not detected (FIG. 4C). By contrast, the examination of AQP4-specific T cells revealed a significantly reduced frequency of Treg in NMO patients in response to rhAQP4, but not to p61-80 (FIG. 4D).

FIG. 4A-4D. AQP4 p61-80-specific T cells exhibit a proinflammatory bias.

PBMC were stained with CFSE and cultured for 10 d with AQP4 peptides (10 μg/ml) or rhAQP4 (5 μg/ml). (Panel A) CD4⁺CFSE^(low) proliferating T cells were analyzed for IL-17 and IFN-γ production by intracellular staining after stimulation with PMA/Ionomycin for 5 h. (Panel B) Frequencies of IL17⁺IFN-γ⁻, IL17⁺IFN-γ⁺ and IL17⁻IFN-γ⁺ were examined among proliferating p61-80-specific CD4⁺ T cells (n=8 NMO and n=5 HC), p156-170-specific CD4⁺ T cells (n=6 NMO and n=3 HC) and rhAQP4-specific CD4⁺ T cells (n=6 NMO and n=5 HC). Frequencies of IL-17- and IFN-γ-single positive T cells were used to calculate Th17/Th1 ratio. (Panel C) PBMC were examined by FACS for expression of Treg markers including CD4, CD127 and CD25. (Panel D) CFSE-labeled PBMC were cultured for 10 d with AQP4 p61-80 (10 μg/ml) or rhAQP4 (5 μg/ml). Proliferating CD4⁺ T cells (CDI>2) were examined by FACS for expression of CD25^(high), defined as the top half of CD25⁺ cells, and Foxp3 (n=8 NMO p61-80, n=6 HC p61-80, n=7 NMO rhAQP4 and n=5 HC rhAQP4). Box-and-whisker plots include the median, distribution and range. **P<0.01 Mann-Whitney U test.

Example 4 Monocytes from NMO Patients Exhibit Pro-Inflammatory Polarization

Antigen presenting cells (APC), including monocytes and other myeloid cells, express costimulatory molecules and secrete specific cytokines that participate in activation and promote lineage commitment of antigen-specific T cells. In this regard, IL-6 is critical for Th17 differentiation (Acosta-Rodriguez E V, et al. Nat. Immunol. 2007 September; 8(9):942-9.). Previous studies have indicated that serum IL-6 levels are elevated in NMO patients (Uzawa A, et al. Mult Scler. 2010 December; 16(12):1443-52.). Since AQP4 p61-80-specific T cells from NMO patients exhibited Th17 polarization, whether there were alterations in expression of costimulatory molecules or increased production of IL-6 by myeloid APC was addressed. In comparison to HC, there was no evident change in frequency of peripheral blood monocytes. However, increased expression of CD40 and CD80 (FIG. 5A; histogram for healthy control is located in between the histograms for isotype and NMO patient), costimulatory molecules that can be associated with pro-inflammatory T cell polarization was observed (Katzman S D, et al., J. Immunol. 2011 Apr. 15; 186(8):4668-73; Kuchroo V K, et al., Cell. 1995 Mar. 10; 80(5):707-18). The frequency of IL-6-producing monocytes was similar in NMO patients and HC. Nevertheless, there were both relative and absolute increases of intracellular IL-6 production after LPS stimulation in monocytes from NMO patients (FIGS. 5B, C). No such differences were observed in expression of IL-10 and IL-10. These results indicate that in addition to the known involvement of adaptive immunity, phenotypic changes of cells within the innate immune system may also contribute to NMO pathogenesis.

FIG. 5A-5C. CD14⁺ monocytes from NMO patients exhibit increased expression of certain co-stimulatory molecules and production of IL-6. (Panel A) PBMC were rested for 4 h at 37° C. Expression of co-stimulatory (CD80, CD86 and CD40) and MHC class II molecules was analyzed by FACS gating on the CD14 population (n=8 NMO and n=8 HC). Isotype is indicated by grey histogram; healthy control and NMO patient histograms for expression of CD86 and HLA-DR were similar; for CD80 and CD40 expression the histogram for healthy control is present in between the histograms for isotype and NMO patient. As such, NMO patients exhibited a higher expression of CD80 and CD40 compared to healthy control. (Panels B and C) PBMC were stimulated with LPS (1 μg/ml) for 4 h. Expression of IL-6 in CD14⁺ monocytes was analyzed by ICS, before and after LPS stimulation. In (Panel C), horizontal lines indicate mean values; in (Panel A) and (Panel B) error bars represent SEM. *P<0.05, **P<0.01 Mann-Whitney test. 

1. A composition comprising: a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: Leu-Pro-X¹-X²-Met-X³-X⁴-Ile-X⁵-X⁶

wherein the peptide is up to 50 amino acids in length, and wherein X¹ is Val (V) or Ile (I), X² is Ser (S) or Asp (D), X³ is Val (V), Ile (I), or Gly (G), X⁴ is Leu (L) or Ile (I), X⁵ is Met (M) or Ser (S), and X⁶ is Leu (L), Val (V), or Ala (A).
 2. The composition of claim 1, wherein: X¹ is Val (V), X² is Ser (S) or Asp (D), X³ is Val (V), X⁴ is Leu (L), X⁵ is Ser (S), and X⁶ is Leu (L).
 3. A composition comprising: a peptide comprising a contiguous stretch of amino acids having the consensus amino acid sequence: LPVXMVLISL

wherein the peptide is up to 50 amino acids in length, and wherein X is Asp or Ser.
 4. A composition comprising a peptide comprising a contiguous stretch of amino acids having the sequence: GILYLVTPPSVVGGLGVTMV

wherein the peptide is up to 50 amino acids in length.
 5. A composition comprising a peptide comprising a contiguous stretch of amino acids having the sequence: SMNPARSFGPAVIMGNWENH

wherein the peptide is up to 50 amino acids in length.
 6. A composition comprising a peptide comprising a contiguous stretch of amino acids having the sequence: AGHGLLVELIITFQL

wherein the peptide is up to 50 amino acids in length.
 7. A composition comprising a peptide comprising a contiguous stretch of amino acids having the sequence: RFKEAFSKAAQQTKGSYMEV

wherein the peptide is up to 50 amino acids in length.
 8. The composition of claim 1, wherein the peptide is 5-30 amino acids in length.
 9. The composition of claim 1, wherein the peptide is 10-20 amino acids in length.
 10. A method of diagnosing Neuromyelitis Optica (NMO) in a subject, the method comprising: contacting a sample from the subject with a peptide of claim 1; and measuring the number of T cells, wherein an increase in the number of T cells as compared to a control indicates that the subject has NMO.
 11. The method of claim 10, wherein the T cells are T helper 17 (Th17) T cells.
 12. The method of claim 10, wherein the T cells are CD4⁺ T cells.
 13. The method of claim 10, wherein the peptide is 5-30 amino acids in length.
 14. The method of claim 10, wherein the peptide is 10-20 amino acids in length.
 15. A method for screening for candidate agents for inhibiting proliferation of T cells, the method comprising: contacting a T cell obtained from a subject having Neuromyelitis Optica with: a peptide claim 1, and a candidate agent; measuring the number of T cells, wherein a decrease in the number of T cells as compared to a control indicates that the candidate agent inhibits proliferation of T cells.
 16. The method of claim 15, wherein the T cells are T helper 17 (Th17) T cells.
 17. The method of claim 15, wherein the T cells are CD4⁺ T cells.
 18. The method of claim 15, wherein the peptide is 5-30 amino acids in length.
 19. The method of claim 15, wherein the peptide is 10-20 amino acids in length.
 20. A method for inducing immune tolerance to AQP-4 protein and fragments thereof in a subject, the method comprising: administering an effective dose of the composition of claim 1 to a subject, wherein the administering the peptide induces immune tolerance to AQP-4 protein and fragments thereof in the subject.
 21. The method of claim 20, wherein the peptide is 5-30 amino acids in length.
 22. The method of claim 20, wherein the peptide is 10-20 amino acids in length. 